[R-390] R-390 VFO

Mon, 22 Dec 2003 20:09:47 -0500

How do you know its the VFO and not something else?  Did you look at the VFO
output level?  Or if the radio just quits receiving, it could be some oher
things.  If you are sure it's the VFO, look at the filament.  All the
oscillator filaments are regulated through the IF module's 3TF7 "ballast"
tube.  If that tube is flaky, or the IF connector is loose,  it can cause
the oscillators to shut down due to loss of filament voltage.  May be heat
related... could be a component beaking down with increased temperature.
You could try this:   Let it warm up, when it quits, use some freeze spray
(from Radio Shack) to cool own different areas.. such as the compartment
underneath the tube...if it starts up again, then something is bad under or
around the tube socket.  If it's something inside the sealed can then that's
another matter.  Also, tighten the screws holding the tube socket, they
could be loose.  Hopefully it's not a cracked coil slug expanding as it
heats.
----- Original Message ----- 
From: "David Hallam" <[email protected]>
To: "R-390 List" <[email protected]>
Sent: Monday, December 22, 2003 8:50 AM
Subject: [R-390] R-390 VFO


> I am looking for advice.
>
> The VFO in my R-390 has quit working.  From a completely cold start, it
will
> for a minute or two and then quit.  I have done the obvious of checking
the
> tube; it tested OK, substituting a couple of different ones, and checking
> the connection in the power and RF sockets.
>
> Any advice on where to start looking for the problem?
>
> David KC2JD
>
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